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Posted: August 24, 2009

Nanotechnology speeds desalination

(Nanowerk News) A team of nanotechnology researchers from The Australian National University have discovered a way to remove salt from seawater using nanotubes made from boron and nitrogen atoms that will make the process up to five times faster.

With 25 percent of the world’s population currently affected by water shortages, researchers Dr Tamsyn Hilder, Dr Dan Gordon and group leader Professor Shin-Ho Chung from the Computational Biophysics Group at the Research School of Biology at ANU have come up with a way to eliminate all salt from seawater whilst maintaining high water flow rates. Their results have been published in the journal Small ("Salt Rejection and Water Transport Through Boron Nitride Nanotubesr").

With population growth and climate change limiting the world’s fresh water stores, desalination and demineralisation are fast becoming feasible solutions. However, there is an urgent need to make the process of desalination more effective and less costly than current methods. Nanotechnology-based water purification devices, such as those proposed by Hilder, Gordon and Chung, have the potential to transform the field of desalination.

“Boron nitride nanotubes can be thought of as a hollow cylindrical tube made up of boron and nitrogen atoms,” said Dr Hilder. “These nanotubes are incredibly small, with diameters less than one-billionth of a meter, or 10,000 times smaller than the thickness of a single strand of human hair.

“Current desalination methods force seawater through a filter using energies four times larger than necessary. Throughout the desalination process salt must be removed from one side of the filter to avoid the need to apply even larger energies.

“Using boron nitride nanotubes, and the same operating pressure as current desalination methods, we can achieve 100 percent salt rejection for concentrations twice that of seawater with water flowing four times faster, which means a much faster and more efficient desalination process.”

Hilder, Gordon and Chung use computational tools to simulate the water and salt moving through the nanotube. They found that the boron nitride nanotubes not only eliminate salt but also allow water to flow through extraordinarily fast, comparable to biological water channels naturally found in the body.

“Our research also suggests the possibility of engineering simple nanotubes that mimic some of the functions of complex biological nanotubes or nanochannels,” said Professor Chung, and work is continuing to investigate these possibilities further. These devices, once successfully manufactured, may be used for antibiotics, ultra-sensitive detectors or anti-cancer drugs.